This invention concerns devices for expanding radial seals to establish compression of the seal against the wall of a surrounding bore. A common use for such devices is with pipe to manhole seals of a type described in U.S. Pat. No. 4,478,437 by the present inventor issued on Oct. 23, 1984 for a "Radially Expandable Locking Sleeve Device" in which an elastomeric sleeve is clamped at one end to the pipe and is expanded outwardly at the other end to create a fluid tight seal against a hole in a manhole structure.
U.S. Pat. No. 5,150,927 by the present inventor issued on Sep. 29, 1992 describes a toothed end split band which is expanded with a special hinged tool, a toothed locking portion holding the band ends in their expanded condition.
A 1995 product brochure for a PRESS-BOOT.TM. of the Press-Seal Gasket Corporation describes a more refined version of this design.
See also U.S. Pat. No. 4,215,868 by the present inventor and U.S. Pat. No. 4,711,455 to Ditcher.
In these patents, the split expansion band is expanded by almost purely circumferential motion in spreading the ends with a hydraulically-operated expander. Friction between the band and the seal becomes very great due to the purely circumferential sliding motion taking place, particularly as the radial forces increase.
In most of these designs, the teeth are ratcheted apart as band expansion takes place. As the friction forces increase as described, the locking teeth may be deformed and fail.
U.S. Pat. No. 3,958,313 issued on May 25, 1976 for a "Method, Apparatus and Product for Improved Pipe to Manhole Sealing" describes an expandable metal band having toggle sections which are moved overcenter by a conventional hydraulic jack. While this approach does not require special expanding devices, the toggle sections may move too far overcenter. This creates a peaked condition which may lead to gaps on either side creating leaks past the seal.
Some of the other expanding sleeve designs described above also create discontinuities on their perimeters affecting sealing.
It is the object of the present invention to provide an expansion band configuration which reduces frictional loads and does not require specialized equipment for installation and which insures an effective seal around the seal perimeter.